Throttle valve control apparatus of internal combustion engine and automobile using the same

ABSTRACT

The invention provides a throttle valve control apparatus provided with a throttle sensor which is in trouble at a low possibility and has a long service life, whereby an accurate output of a throttle opening degree can be obtained. The throttle valve control apparatus of an internal combustion engine has a throttle opening degree sensor constituted by an non-contact sensor using hole elements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/762,328 filed Jan. 23, 2004, which is a continuation of U.S.application Ser. No. 10/747,983, filed Dec. 31, 2003, now U.S. Pat. No.7,152,581 which is a continuation of U.S. application Ser. No.09/794,209, filed Feb. 28, 2001 now U.S. Pat. No. 6,701,892 and claimspriority of Japanese patent application no. 2000-110540, filed Apr. 6,2000. The entire disclosure of these documents are herein expresslyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present application relates to a throttle valve control apparatusfor controlling a flow amount of intake air of an internal combustionengine and a motor vehicle.

2. Description of the Prior Art

An electrical control type throttle apparatus opening and closing athrottle valve of an internal combustion engine by a motor-drivenactuator (for example, a direct current motor, a stepping motor, atorque motor and a brushless motor) is put into practice.

The electrical control type throttle apparatus is structured such as tocontrol an optimum throttle valve angle (throttle valve opening degree)corresponding to an engine state on the basis of an opening degreesignal of an accelerator pedal and a traction control signal. For thispurpose, a sensor for detecting an angle of the throttle valve,so-called a throttle sensor (which may be sometimes called as an openingdegree meter or a throttle position sensor) is attached to a throttlebody.

A potentiometer system is generally employed in the throttle sensor, anda brush (a sliding element) rotating together with a throttle valveshaft slides on a resisting body, thereby outputting a potentialdifference signal (a sensor detecting signal) corresponding to athrottle valve opening degree (for example, refer to Japanese UnexaminedPatent Publication No. 9-32588).

This kind of conventionally used throttle sensor is structured such thatthe brush is in contact with a variable resistance and a conductorformed on a resistance base plate so as to slide thereon. Accordingly, aservice life of the sensor is short and the sensor is frequently introuble. A double route of sensor is employed so as to detect a troubleof sensor and mutually back up, however, this can not basically solvethe problem.

Further, since the trouble mentioned above is generated in theconventional motor vehicle at a high possibility, and a controlparameter is controlled by an output of the sensor having a shortservice life, an accuracy for operating and controlling the internalcombustion engine is low.

There has been known Japanese Patent No. 2845884 as a structure fordetecting the opening degree of the throttle valve in a non-contactmanner.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a throttle valvecontrol apparatus provided with a throttle sensor which is in trouble ata low possibility and has a long service life.

In particular, there is suggested some structures for compactlyattaching a non-contact type sensor to a throttle control apparatus soas to constitute a part of the apparatus.

Further, there is suggested structures for removing a magnetic noise anda bad influence against a magnetic characteristic.

Further, another object is to improve a throttle sensor corresponding toone of elements for controlling control parameters of an internalcombustion engine so as to improve an operation control accuracy of theinternal combustion engine.

In order to achieve the objects mentioned above, the present inventionproposes the following throttle valve control apparatuses and motorvehicles.

In accordance with a first aspect of the present invention, there isprovided a throttle valve control apparatus of an internal combustionengine comprising:

a throttle valve axis rotated by a motor-driven actuator;

an alternate magnet mounted to the throttle valve axis;

a cover to which an element for detecting a change of magnetic flux ofthe alternate magnet is mounted;

the cover being mounted to a throttle body to which the motor-drivenactuator is mounted; and

an output of the element constituting a function of an opening degree ofthe throttle valve.

In accordance with a second aspect of the present invention, there isprovided a throttle valve control apparatus of an internal combustionengine comprising:

a throttle body provided with a throttle valve controlling an amount ofintake air;

a throttle sensor detecting a rotational angle of an axis to which thethrottle valve is mounted; and

a motor-driven actuator in which a command value is adjusted inaccordance with an electric signal output from the throttle sensor,

wherein the throttle sensor comprises:

an element mounted to one end of the throttle valve axis; and

another element attached to a cover member fixed to the throttle body soas to cover the axial end portion, and

wherein a magnetic physical amount between the pair of elements isvaried in accordance with a change of the rotational angle of thethrottle axis, and the element mounted to the cover member outputs anelectric signal relating to the rotational angle of the axis in responseto the change of the magnetic physical amount.

In accordance with a third aspect of the present invention, there isprovided a motor vehicle comprising:

an element outputting an electric signal relating to an opening degreeof a throttle valve on the basis of a magnetic signal of a magnetmounted to an axial end of the throttle valve,

wherein a control parameter of an engine is adjusted in accordance witha change of the electric signal output from the element.

In accordance with a fourth aspect of the present invention, there isprovided a throttle control apparatus of an internal combustion enginestructured such as to transmit a rotation of a motor to a throttle valveaxis via a gear fixed to the throttle valve axis,

wherein a rotational angle of the throttle valve axis is detected by amagnetic type throttle sensor comprising a magnet and a hole element,and the gear is formed by a resin material.

In accordance with a fifth aspect of the present invention, there isprovided a throttle valve control apparatus of an internal combustionengine structured such that a rotary axis of a motor and a throttlevalve axis are arranged in parallel and a rotation of the rotary axis ofthe motor is transmitted to the throttle valve axis via a reductiongear,

wherein a magnetic type throttle sensor comprising a magnet and a holeelement is mounted so as to be capable of detecting a rotational angleof the throttle valve axis, and

wherein a rotary axis of a gear positioned in a middle of a torquetransmission path between the rotary axis of the motor and the throttlevalve axis is formed by a magnetic material.

In accordance with a sixth aspect of the present invention, there isprovided a throttle valve control apparatus of an internal combustionengine structured such as to detect a rotational angle of a throttlevalve driven by a motor,

wherein a magnet is mounted to the throttle valve axis;

wherein hole elements are arranged at positions facing to each otherwith respect to the magnet and a stator corresponding to a magnetic pathis attached between the hole elements, and

wherein the motor is mounted to a position a uniform distance apart fromthe both hole elements.

In accordance with a seventh aspect of the present invention, there isprovided a throttle valve control apparatus of an internal combustionengine structured such that a sensor for detecting a rotational angle ofa throttle valve driven by a motor is provided and a rotary axis of themotor and the throttle valve axis are arranged in parallel,

wherein a magnet is mounted to the throttle valve axis,

wherein hole elements are arranged at positions facing to each otherwith respect to the magnet and a stator corresponding to a magnetic pathis attached between the hole elements, and

wherein the both hole elements are arranged out of a circular arc havinga radius corresponding to a distance between the rotary axis of themotor and a center of the throttle valve axis.

In accordance with an eighth aspect of the present invention, there isprovided a throttle valve control apparatus of an internal combustionengine comprising:

a magnet mounted to a throttle valve axis to which a throttle valve ismounted; and

a cover fixed to a throttle body so as to cover the magnet portion,

wherein a hole element sensitive to a change of a magnetic physicalamount of the magnet and a signal processing circuit converting anoutput of the hole element into a predetermined electric signal aremounted to the cover.

In accordance with a ninth aspect of the present invention, there isprovided a throttle valve control apparatus of an internal combustionengine structured such that a rotary axis of a motor and a throttlevalve axis are arranged in parallel and a rotation of the rotary axis ofthe motor is transmitted to the throttle valve axis via a reductiongear,

wherein a cover is mounted to a throttle body so as to cover thereduction gear, and

wherein a magnetic type throttle sensor comprising a magnet and a holeelement is mounted between an end surface of a gear fixed to thethrottle valve axis and the cover so as to be capable of detecting arotational angle of the throttle valve axis.

In accordance with a tenth aspect of the present invention, there isprovided a throttle valve control apparatus of an internal combustionengine comprising:

a magnet mounted to an end portion of a throttle valve axis rotated by amotor;

an element detecting a rotational angle of the throttle valve axis incooperation with the magnet; and

a spring holding the magnet at a predetermined opening position ofopening degree when energizing of the motor is shut out, the springbeing attached to a periphery of the throttle valve axis.

In accordance with an eleventh aspect of the present invention, there isprovided a throttle valve control apparatus comprising:

a magnet mounted to a throttle valve axis rotated by a motor;

an element detecting a rotational angle of the throttle valve axis incooperation with the magnet; and

the element being constituted by two components arranged under amagnetic influence of the magnet so as to be backed up by each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a throttle valve control apparatusin accordance with an embodiment of the present invention;

FIG. 2 is another cross sectional view of a throttle valve controlapparatus in accordance with an embodiment of the present invention;

FIG. 3 is an exploded perspective view of a throttle valve controlapparatus in accordance with an embodiment of the present invention;

FIG. 4 is an exploded perspective view of a throttle valve controlapparatus in accordance with an embodiment of the present invention asseen from another angle;

FIG. 5 is a view for explaining a feature of a structure of theembodiment;

FIG. 6 is a view showing a throttle valve axis assembly; and

FIGS. 7A and 7B are views for explaining a positional relation between amotion of a magnet and a hole element.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will be given below of an embodiment in accordance withthe present invention with reference to the accompanying drawings.

As shown in FIG. 1, an electronic control type throttle valve apparatus(a throttle valve apparatus) is mainly constituted by a throttle body(hereinafter, which may be simply called as a body) 1, a throttle valve4, a motor (a throttle valve drive apparatus; a motor-driven actuator)22 for driving the throttle valve 4, a reduction gear mechanism 100, asensor (a throttle sensor) 80 measuring an opening angle (an openingdegree) of the throttle valve 4, that is, a rotational angle of thethrottle valve axis 3, and a cover 16 protecting the throttle valve axis3, the motor 22 and the reduction gear mechanism 100.

The body 1 is constituted by integrally forming a receiving portion (anintake bore) 2 of the throttle valve 4 and a receiving portion (a motorhousing) 1 c of the motor 22.

The throttle valve 4 is mounted to the throttle valve axis 3 by means ofa screw 5, and the axis 3 is supported by bearings 6 and 26 provided inthe body 1.

In accordance with the present embodiment, the bearing 6 is formed as aball bearing, and the bearing 26 is formed as a cap-shaped planebearing. The reason and details thereof will be described later. Theball bearing 6 is attached to a bearing boss 1 a via a seal ring 8.Further, an inner ring 6 a of the ball bearing 6 is pressure inserted toan outer periphery of the throttle valve axis 3, and an outer ring 6 bis transition fitted to an inner periphery of the bearing boss 1 a.

In the throttle valve axis 3, only one end protrudes out of a side wallof the body 1. Then, a spring 10, a lever 9, a spring 11 and a finalstage gear (a driven gear) 12 of the reduction gear mechanism 100 areattached to one end of the throttle valve axis protruding out of theside wall.

Throttle valve relating parts (hereinafter, called as a throttle valvemechanism) such as the throttle valve axis 3, the reduction gearmechanism 100, the motor 22 and the like are received in a receivingportion (a case) 1 d formed on a side wall of the body 1, and thereceiving portion 1 d is covered by a synthetic resin cover 16. Theplane bearing 26 is attached in accordance with a pressure insertion.

That is, the throttle valve mechanism is arranged so as to be protectedby one cover 16, an opening (an opening for mounting the motor) 1 c′ ofa motor housing 1 c is positioned so as to face within the receivingportion 1 d, the motor 22 is received in the housing through theopening, and an end bracket 22 a of the motor is fixed in the peripheryof the opening 1 c′ by a screw 37 (refer to FIGS. 3 and 4).

A motor terminal 23 provided in the end bracket 22 a is positioned nearone line of the side wall in the receiving portion 1 d, is arranged soas to be directed to the cover 16 side, and is connected to a relayterminal 24 a provided in the cover 16 side via a relay connector 33.The relay connector 33 can employ various kinds of aspect. In thepresent embodiment, a sleeve made of a conductive material is used asthe relay connector 33, slits 34 and 35 having shifted directions at 90degrees are provided in both ends thereof, and the relay terminal 24 aand the motor terminal 23 are inserted to the slit. The terminals 24 aand 23 also have shifted directions at 90 degrees in correspondence tothe directions of the slits 34 and 35.

The motor 22 is driven in response to an acceleration signal relating toa pedaling amount of an acceleration pedal, a traction signal, a uniformspeed traveling signal, and an idle speed control signal, and a power ofthe motor 22 is transmitted to the throttle valve axis 3 via thereduction gear mechanism 100 (the motor pinion 21, middle gears 20 andthe final stage gear 12). The pinion 21 is mounted to a motor shaft 27,and the middle gears 20 are freely fitted to a conductive shaft 19adhered to the throttle body 1. A gear 20 a having a larger diameteramong the middle gears 20 is engaged with the pinion 21 and a gear 20 bhaving a smaller diameter is engaged with the gear 12.

The final stage gear 12 is a fan-shaped gear as shown in FIGS. 3 and 4.

A description will be given of a relation between the gear 12 and thelever 9. The gear 12 has a hole 12 h for passing one end of the throttlevalve axis 3 therethrough as shown in FIG. 3, the hole 12 h is formed ina shape capable of engaging with one end 3 a (having at least two flatsurfaces) of the throttle valve axis and is integrally rotated with thethrottle valve axis.

The lever 9 is freely fitted to an outer periphery (a circumferentialsurface) of the throttle valve axis 3, however, is engaged so as to betogether attracted to the gear via the spring 11. For example, aprojection denotes by reference symbol 12 f in FIG. 4 is engaged with aprojection (not shown) of the lever 9. The projection 12 f is formedinside the gear 12.

The spring 10 corresponds to a return spring for the throttle valve, oneend thereof is engaged with a spring engaging portion (not shown)provided in the body 1, and another end thereof is engaged with thelever 9.

The spring 10 applies a return force to the throttle valve axis via thelever 9 and the gear 12, and further, constitutes a so-called defaultopening degree setting mechanism which has been already known, incooperation with the spring 11 and the lever 9.

The default opening degree setting mechanism is structured such as tokeep an initial opening degree of the throttle valve 4 at a time ofturning off an engine key (in other words, at a time when themotor-driven actuator 22 is not energized) to a predetermined openingdegree larger than a full close position.

Between the default opening degree position to a full open controlposition, the throttle valve opening degree is determined incorrespondence with a balance between a torque of the motor 22 and avalve closing force of the spring (the return spring) 10.

In the case of controlling so as to make the throttle valve openingdegree smaller than the default opening degree, a motion of the lever 9is restricted by a default opening degree stopper (not shown) and thecontrol operation is performed by rotating only the gear 12 and thethrottle valve axis 3 in a full closing direction against the force ofthe spring 11.

A movable side stopper 12 d provided in one line of the fan-shaped gear12 is brought into contact with a full close stopper (not shown) forrestricting a mechanical full close position of the throttle valve,whereby a full close position is determined.

With respect to a material of the gear 12 in accordance with the presentembodiment, a center portion thereof is formed by a metal plate 12 a,and a portion 12 b forming teeth and the other portions are integrallyformed by a synthetic resin (a reinforced plastic).

In this case, the metal plate 12 a is insert molded to the resin portionof the gear 12.

A side end of the gear 12 of the magnet 82 faces to the resin portion ofthe gear.

Accordingly, it is possible to prevent a magnetic flux of the magnet 82from being leaked to the gear 12.

The metal plate 12 a in a center portion of the gear 12 is pressed tothe throttle body 1 a side by a magnet holder 81, however, since themagnet holder 81 itself is made of a resin, the magnetic field is notleaked even if the magnet holder 81 is in contact with the metal plate12 a.

The movable side stopper 12 d formed in one of cut end surfaces of thegear 12 is integrally connected to the metal plate 12 a.

The movable side stopper 12 d is made of a metal for the purpose ofachieving an abrasion resistance and an impact resistance. That is,mechanical full close position of the throttle valve becomes a referencepoint on control, and the stopper element 12 d is brought into contactwith the full close stopper 25 in a fixed side at least one time atevery operation starting times or operation finishing times.Accordingly, the movable side stopper 12 d is made of a metal so as toresist against a comparatively high collision frequency.

Reference symbol 12 i denotes a guide for engaging the gear 12 with thelever 9.

The resin magnet holder 81 is pressure inserted and fixed to the frontend of the throttle valve axis 3, and the magnet 82 is integrallyattached to the magnet holder 81 in accordance with a molding process.

An end portion of the magnet holder 81 presses the end surface of thegear 12 to a stepped portion 3 d side of the throttle shaft 3, andcommonly serves to prevent the gear 12 from being taken out.

A circuit board 84 of the throttle sensor 80 is fixed to a positionopposing to the end portion of the throttle axis 3 on the inner surfaceof the cover 16 by a welding pin 86.

A pair of semicircular stators 83 are fixed to the circuit board 84 soas to surround a periphery of the magnet 82 in such a manner as to faceto each other with keeping a predetermined interval 87. Referencenumeral 85 denotes a guide of the stator 83 integrally provided in thecircuit board 84.

Hole elements 86 are mounted to a gap 87 portion between a pair ofsemicircular stators 83.

Three terminals of the hole elements 86 are mechanically held to thecircuit board 84 and are connected to a signal processing circuit suchas an amplifier or an analogue/digital converter (not shown) arranged inthe circuit board 84.

The signal processing circuit arranged in the circuit board 84 isconnected to a conductor 24 integrally molded with the cover 16, and cantransmit a signal to an external apparatus via an electric terminal 40(connected to the conductor 24) of the connector 16 b integrally formedwith the cover.

The hole element 86 detects a change of the magnetic field and generatesa hole voltage when the throttle valve axis 3 rotates and the magnet 82rotates.

The voltage is transmitted to the external circuit via the conductor 24and the terminal 40 after being amplified by the amplifier or signalconverted (including an amplification) by the analogue/digitalconverter.

An engine control unit (not shown) of a motor vehicle is provided with acoupler connected to the connector 16 b and a signal line, and thesignal from the terminal 40 is input to the control unit.

The control unit corrects a fuel and an opening degree of a throttlevalve corresponding to the control parameters and controls a speedchange point of an automatic transmission, on the basis of a throttleopening degree and a vehicle speed detected in correspondence to achange of magnetic field corresponding to a magnetic physical amount ofthe magnet 82.

Further, the spring 11 urges the gear 12 in a throttle valve openingdirection so as to forcibly open the magnet 82 of the sensor to apredetermined opening degree position, when the energizing of the motor12 is shut out.

Accordingly, in the motor vehicle provided with the throttle controlapparatus in accordance with the present embodiment, the controlparameters of the engine are adjusted in correspondence to the change ofthe electric signal which the hole element 86 outputs in connection withthe opening degree of the throttle valve in response to the magneticsignal of the magnet mounted to the axial end of the throttle valve.

Since the sensor is a non-contact type, the opening signal of thethrottle valve 4 corresponding to the change of the electric signalwhich the hole element 86 outputs is not exposed to a secular change somuch, so the it is possible to accurately adjust the control parametersof the internal combustion engine for a long period.

A description will be given of a principle of the sensor with referenceto FIG. 7.

The magnet 82 corresponding to a rotor of the throttle sensor 80 isfixed to the magnet holder 81 in a state of facing a pair of arc-shapedmagnets mutually having different polarities to each other.

When the magnet holder 81 is fixed to the throttle valve 3 and thethrottle valve axis 3 is rotated, bonding surfaces of both of themagnets are relatively rotated with respect to the hole element. FIG. 7shows a change of a magnetic line of force in this state.

A pair of hole elements 86 placed in the bonding surface portion of themagnetic pole output a signal forming a function of a rotational anglein response to the change of the magnetic line of force generated incorrespondence to the change of the rotational angle of the throttlevalve axis 3.

Since the gear 12 is made of a synthetic resin, the magnetic fieldgenerated by the magnet 82 is not badly influenced by the gear 12.

In the embodiment, the center portion fitted to the throttle valve axis3 is made of a metal, however, a magnetic bad influence is furtherreduced by forming all the elements by a synthetic resin.

Since the magnetic field is not shifted even when the shape of the gear12 is an irregular shape such as a fan shape, a sensitive characteristicof the hole element 86 can be uniformly obtained without relation to anangle of rotation of the throttle axis.

As shown in FIG. 5, the hole element 86 is mounted in an outer portionof an area of a circular arc S drawn around a center of rotation of themotor by setting a size between a center of the rotary axis of the motorand a center of rotation of the throttle to a radius.

As a result, the hole element 86 is hard to be affected by anelectromagnetic influence caused by a change of a drive current of themotor, and a detecting accuracy of the hole element 86 is hard to bedeteriorated.

Since the structure is made such that the stator 83 is mounted to thecircuit board 84 so as to be fixed to the inner surface of the cover 16,an assembling operation of the stator 83 can be easily performed.

In this case, it is possible to directly fix the stator to the cover 16.

In this case, the stator is fixed with shifting the control circuit fromthe stator, however, there is an advantage that a size in an axialdirection can be shortened.

Since the rotational support axis 19 of the middle gear 20 positionedbetween the motor 22 and the magnetic type non-contact sensor 80 is madeof a magnetic material, it is possible to expect an effect of shieldingan electromagnetic influence caused by the change of the drive currentof the motor 22 by the rotational support axis 19, so that the holeelement 86 is hard to be affected by the electromagnetic influence ofthe motor 22, and a detecting accuracy of the hole element 86 is hard tobe deteriorated.

As shown in FIG. 6, since it is possible to assemble the throttle valveaxis 3, the springs 10 and 11, the lever 9, the final stage gear 12, themagnet holder 81 and the magnet 82 to the throttle body 1 as asub-assembly, an assembling operation can be easily performed.

In accordance with the present invention, it is possible to assemble thenon-contact type sensor in the throttle body in a compact manner.

In accordance with another invention, it is possible to arrange thenon-contact type throttle sensor between the cover of the throttle bodyand the gear in a compact manner.

Further, in accordance with the other invention, it is possible toassemble the non-contact type throttle sensor of the electromagneticsystem in the throttle body by the structure which is hard to beaffected by the electromagnetic noise.

Since it is possible to adjust the control parameters of the engine onthe basis of the throttle opening degree signal which has a littlesecular change, a motor vehicle having a high control accuracy can beobtained.

1. A throttle valve control apparatus of an internal combustion enginecomprising: a throttle valve axis; a final gear fixed to said throttlevalve axis and transmitting a driving force of a motor to said throttlevalve axis; a throttle body supporting said throttle valve axis; athrottle sensor detecting a rotation angle of said throttle valve axis;and a cover attached to said throttle body and covering said final gear,wherein said throttle sensor is of a magnetic type having a magnet and aHall element detecting a change of a magnetic flux of said magnet, andwherein said magnet and said Hall element are arranged between a surfacein a side in which a gear fixed to said throttle valve axis faces tosaid throttle body, and an inner surface of said cover.
 2. A throttlevalve control apparatus of an internal combustion engine as claimed inclaim 1, wherein said magnet is attached to said throttle valve axis,and said Hall element is attached to said cover.
 3. A throttle valvecontrol apparatus of an internal combustion engine as claimed in claim1, wherein an output of said Hall element is a function of an openingdegree of said throttle valve.
 4. A throttle valve control apparatus ofan internal combustion engine as claimed in claim 1, wherein a commandvalue of said motor is regulated on the basis of an electric signaloutput by said throttle sensor.
 5. A throttle valve control apparatus ofan internal combustion engine as claimed in claim 1, wherein said gearis constituted by a metal plate fixed to said throttle valve axis, and asynthetic resin portion forming teeth, and said synthetic resin portionis integrally formed with said metal plate by insert molding said metalplate.
 6. A throttle valve control apparatus of an internal combustionengine as claimed in claim 1, wherein a rotation axis of said motor isarranged in parallel to said throttle valve axis, a rotation of therotation axis of said motor is transmitted to said throttle valve axisvia a reduction gear, and a support axis of an intermediate gearpositioned at the midpoint of a torque transmission path between therotation axis of said motor and said throttle valve axis.
 7. A throttlevalve control apparatus of an internal combustion engine as claimed inclaim 1, wherein said Hall element and a signal processing circuitconverting an output of said Hall element into a predetermined electricsignal are operatively attached to said cover.
 8. A throttle valvecontrol apparatus of an internal combustion engine as claimed in claim1, wherein a spring holding said magnet at a predetermined openingdegree position at a time of shutting off the current of said motor isinstalled at a periphery of said throttle valve shaft.
 9. A throttlevalve control apparatus of an internal combustion engine as claimed inclaim 1, wherein said Hall element comprises two elements arranged undera magnetic effect of said magnet and backed up mutually.